The present invention relates to toilets having siphonic outlet traps extending from their bowl. More particularly it relates to improvements in such traps to facilitate bowl cleaning with lower water usage.
Conventional toilets typically have a bowl portion connected to a serpentine outlet passage. An up leg portion of the passage is normally filled with water between flush cycles to “trap” sewer gases downstream thereof, so as to thereby prevent the sewer gases from entering the building interior.
Water is maintained in the bowl and the up leg part of the trapway by an arched portion of the trapway known as a “weir”. A down leg of the trapway which is downstream of the weir is a leg that is designed to develop a siphon once the flushing cycle starts, to help further evacuate the bowl. Downstream of that is usually a cross leg to carry the flow to an outlet and also to help form the siphon in the down leg.
The trapway thus serves multiple purposes. It traps sewer gas, it helps retain water in the bowl prior to flushing, and it then assists in the formation of a siphon during the flush cycle. Achieving all of these functions is relatively straightforward when a large volume of water can be used during a single flush cycle (e.g. 3 gallons). However, primarily for water conservation reasons many jurisdictions now restrict, and consumers prefer not to use, toilets that use that much water per flush. It is now standard for toilets not to use more than 1.6 gallons (6.06 liters) of water per flush cycle.
Achieving effective cleaning when using that little water can be difficult. Hence, some early models of low water usage toilets had problems with cleaning effectiveness, which led to consumers flushing multiple times per visit. Others incorporated relatively expensive devices such as pumps to provide more force to the water that was used. While the art has now begun to develop less expensive ways to achieve effective cleaning with 1.6 gallons of water, there is a regulatory and market desire for toilets to work with even less water per flush.
One impediment to reducing the amount of water used per flush cycle more is that the process of forming the siphon in the siphon leg has in the past used a substantial amount of water. For example, a significant amount of water passed through the trapway before the siphon ever formed. Cutting down on the amount of time it takes to form the siphon is not a simple matter as there is a need to remove air trapped in the down leg and outlet leg, and as initial flow patterns through the trap vary depending on the nature of the waste in the bowl. Further complicating matters is that some purported solutions lead to clogging problems.
Representative of the current trapway art are U.S. Pat. Nos. 1,062,413, 1,132,866, 1,221,359, 1,251,268, 1,964,876, 2,066,883, 3,484,873, 4,246,227, 5,170,515, 5,404,597, 5,706,529, 5,819,326, 5,918,325, 5,983,413, 6,145,138, 6,986,172 and 7,020,908. See also U.S. patent application publication 2003/0213055.
Accordingly, there is still a need for improved trapways, particularly those which permit efficient bowl cleaning with very low levels of water usage per flush.